>
>The other day I send message to this net that included:
>
>"In order to get a good effiency on 28 MHz why not lower the anode impedance
>by inserting an inductance beetween the anode and filter? I see an example
>in my 1991 ARRL HANDBOOK an example:
>
>A tube with 3500 ohms anode impedance and 10 pF output capacitance is
>transformed into 1481 ohms and 16 pF by inserting a 1 uH inductance beetween
>anode and output filter. Will this inductance act as a parasite choke as
>well?"
My guess is probably not better VHF stability. The mla-2500 has several
hundred nH between the anodes and C1. However, on avg. they have
plenty of parasites. The problem it that the extra long anode lead has
many resonances in the VHF range that are above the grid resonance.
>
>I did not get any answer on my very last question from you pi/piL
>specialists. Is this not a better method to get rid of parasitics and at the
>same time get higher output on 10 meters with tubes like the 813 that has a
>high output capacitance??
? The problem with the 813 on 10m seemingly has more to do with internal
L than internal C.
>
cheers, Hans
>
>
>----------
>>FrÂn: measures <measures@vcnet.com>
>>Till: "cd" <bearl@ozemail.com.au>, "AMPS" <amps@contesting.com>
>>?mne: Re: [AMPS] Nichrome/Parasitics/ARRL Handbook 2000
>>Datum: mÂn 7 feb 2000 18.58
>>
>
>>
>>>Those of you that have not picked up, or had a look at the new ARRL
>>>Handbook 2000, there is some mention now of Nichrome Parasitic
>>>suppressors. It reads as follows in chapter 13.26.
>>>
>>>"Some designers use nichrome or other resistance wire for L2, but there is
>>>no credible evidence of any fundamental difference in importance as a
>>>result." It goes on to say that W4ETO, amplifier manufacturer has never
>>>seen an HF amplifier using modern tubes that could not be made completely
>>>free of VHF parasitics by using one of the simple parasitic suppressor
>>>contruction described above" It does not mention what "advanced"
>>>techniques should be used!
>>>
>>>Anyway for those curious have a read.
>>>
>>Craig -- This was written by Dick Erhorn / W4ETO for the 1995 Handbook,
>>several years before N7WS/Wes' measurements of copper-wire vs
>>resistance-wire suppressors. . My guess is that Dick never read G. W.
>>Fyler's article on parasitic oscillation in the Institute of Radio
>>Engineers' Journal. // Sure, the decrease in VHF Q is only about 41%
>>with resistance-wire VHF parasitic suppressors, however, this might be
>>enough to make a difference.
>>
>>cheers
>>
>>
>>
>>
>>
>>
>>
>>w4ETO
>>
>>>VK3HE
>>>
>>
>>
>>- Rich..., 805.386.3734, www.vcnet.com/measures.
>>
>>
>>--
>>FAQ on WWW: http://www.contesting.com/ampsfaq.html
>>Submissions: amps@contesting.com
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>>Problems: owner-amps@contesting.com
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>>
>>
>
>--
>FAQ on WWW: http://www.contesting.com/ampsfaq.html
>Submissions: amps@contesting.com
>Administrative requests: amps-REQUEST@contesting.com
>Problems: owner-amps@contesting.com
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>
>
- Rich..., 805.386.3734, www.vcnet.com/measures.
--
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